The ultrasound imaging system has been widely used to acquire an image showing an internal organ of a human body for medical diagnosis purposes. The ultrasound imaging system basically incorporates several functional components to perform ultrasound signal transmission and reception, and various subsequent signal processing. For example, transducers are used to transmit ultrasound signals to an internal organ of the human body and to detect echo signals reflected from the body. An ultrasound receive-focusing apparatus is used to receive-focus the reflected echo signals, i.e., to add appropriate time delays to the echo signals and synthesize the delayed echo signals so that output beams are formed.
Among these components, the receive-focusing apparatus is known to be the component that most affects the performance of the ultrasound imaging system. That is, the performance of the ultrasound imaging system depends largely upon that of the receive-focusing apparatus. The size of the hardware for implementing receive-focusing takes up a significant portion of the entire hardware of the system because the receive-focusing apparatus needs to incorporate the same number of channel modules as transducers, each module including an analog-to digital converter, a delay element, a memory element and an apodization element.
Two types of receive-focusing apparatus are known in the art: analogue and digital. Recently, the digital receive-focusing apparatus is being more widely used than the analogue receive-focusing apparatus because it excels over the latter in controlling time delays and performing fine beam focusing, due to the recent developments in digital circuit technology.
Generally, the digital receive-focusing apparatus needs to process ultrasound signals originating from a large number of channels, for example, 32-512 channels to satisfy the resolution requirements for ultrasound imaging systems. As larger numbers of channels are implemented to satisfy higher resolution requirements, a digital receive-focusing apparatus capable of processing even more channel signals is necessary. In order to process a larger number of channel signals, a corresponding number of channel modules must be included in the receive-focusing apparatus, which means that the complexity of the digital receive-focusing apparatus increases.